Conveyor belts are frequently used to transport items from one location to another. A conveyor belt when used as a conveying means normally has a fixed length or run extending between end rollers on which the belt travels and which are located at the beginning and end of travel of the belt. Thus, the conventional belt conveyor has an operative surface or run of fixed length.
There are, however, operations requiring the use of a conveyor belt in which the length of the operative surface or run is required to change. An example of a conveyor belt extending between the beginning and the end of a conveyorized scaling process and in which the length of the operative run is required to periodically change during the course of moving items along a path is found in the reciprocable sealing bar section of an automatic film wrapping machine, such as that used to pack poultry for retail sale. As the speed of processing increases in such a variable length belt run system, the need to keep firm control of the product being packed also becomes increasingly important. In a widely used type of poultry packaging machine, a sheet of heat sealable film is formed into a tube around the product being packed. The tube is then cut and sealed along a line transverse to its center line at a series of locations essentially between successive wrapped items. The cutting and sealing of the film is accomplished by a pair of heated sealing bars which converge onto the film tube and travel with the tube for a selected distance to permit a dwell time sufficient to adequately seal and cut the tube. The heated bars then separate and move backward to their starting position. Such a machine is disclosed in Japanese patent No. 63-33230 to Tadoru Suga for "Operation Control Apparatus Of Seal Mechanism in Packaging Machine And Method Therefor". To allow the sealing bars to first move with and in the direction of the conveyor and then move back, there is disclosed in related Japanese patent application Ser. No. 4-121,444, filed Apr. 15, 1992, a conveyor having a moving gap on its product carrying surface which reciprocates to accommodate the reciprocating sealing bars.
In order to maintain proper control of the product being wrapped in the process of the Saga disclosure and to improve thereupon, it has been found beneficial, according to the present invention, to have continuously driven vertical side conveyor belts which are used to hold the film wrapped package through the time it is sealed and cut off. Therefore, the present invention recognizes that the presence of continuously driven side conveyor belts which essentially elongate as the conveyor gap moves in one direction and contract as the conveyor gap moves in the other direction in order to follow the action of the varying moving gap conveyor surfaces would provide a means for enhancing control of the product being packaged.
Therefore, it is an objective of the present invention to provide a belt conveyor, typically comprising a pair of continuously driven belts between which the product travels, at least one run of which is capable of being changed in operative length.
It is an additional objective of the invention to provide a conveyor, typically comprising a pair of belts between which a product travels, having at least one run which while running continuously in a given direction may be adjusted in length automatically in coordination with a related process such as a sealing process in the same machine in which the conveyor is mounted.
It is a further more specific objective of the invention to provide a conveyor apparatus having a run which is variable in length while operating continuously to transport a product such as a film wrapped poultry product.
These and other objectives will become apparent from the disclosure which follows.